Women at high risk for breast cancer could possibly reduce the incidence of the disease with an estrogen-stopping drug. Anastrozole cuts breast cancer risk by more than 50 percent in women at high risk, according to a recent study.

Breast cancer screenings are recommended for all women, especially those who face a greater risk. Susan G. Komen says a mutation — or a first-degree relative with a mutation — in the BRCA1 or BRCA2 gene, a family history of breast cancer with a family member diagnosed at age 40 or younger, and a personal history of invasive breast cancer, significantly increases a woman’s odds of developing cancer. Breast magnetic resonance imaging (MRI) in combination with mammography, compared to mammography alone, is accurately able to detect breast cancer in certain women at high risk.

While early breast cancer screenings are one of the most popular forms of cancer prevention in a high risk population, researchers suggest the availability of anastrozole could be a promising prevention treatment in post-menopausal women.

Published in the journal The Lancet, a team of researchers from the IBIS II trial, funded by Cancer Research UK and led by Queen Mary University of London, examined the effects of anastrozole on a cohort of post-menopausal women at high risk of developing breast cancer. Approximately 4,000 women between the ages of 40 and 70, from 18 countries, were recruited for the international, double-blind, randomized placebo-controlled trial. To be eligible for the study, the large cohort of women had to be at an increased risk of breast cancer, which was judged on the basis of specific criteria by the researchers.

The participants were considered high risk if they had one of the following criteria: two or more blood relatives with breast cancer, a mother or sister who developed breast cancer before the age of 50, or a mother or sister who had breast cancer in both breasts or a certain high risk type of benign breast disease.

Researchers randomly assigned the women to receive either one milligram dose of anastrozole daily for five years, or they received a matching placebo. Anastrozole, belongs to a class of drugs called aromatase inhibitors, which are responsible for blocking an enzyme involved in the production of estrogen. Unlike tamoxifen, which interferes with a tumor’s ability to respond to estrogen, anastrozole completely cuts off estrogen supply to prevent the growth of tumors.

During the five-year follow-up period, 40 women in the anastrozole group developed breast cancer compared with 85 of those in the placebo group.

"This research is an exciting development in breast cancer prevention. We now know anastrozole should be the drug of choice when it comes to reducing the risk of breast cancer in postmenopausal women with a family history or other risk factors for the disease,” said Professor Jack Cuzick, lead researcher and head of Queen Mary University of London's Center for Cancer Prevention, in the press release.

Anastrozole was not only found to be effective but also to contain fewer side effects than previous drugs, such as tamoxifen. Typically, acute aches and pains have often been associated with estrogen depriving drugs but the researchers noted the reported side effects were only slightly higher than in the placebo group. This suggests the participants’ symptoms were not drug related, and the concern about side effects for this type of drug may have been overstated in the past, wrote the researchers.

These findings highlight aromatase inhibitors could provide a useful prevention alternative for postmenopausal women who face a high risk for breast cancer. Although this treatment does look promising in the prevention of breast cancer, researchers remain skeptical about its availability to the public.

"The challenge will be ensuring drugs like these are actually offered on the NHS, as many eligible women still don't have access to the risk-reducing treatments already recommended in national guidelines,” said Dr. Caitlin Palframan, head of policy at the charity Breakthrough Breast Cancer, The Guradian reports. Researchers are working closely with the NHS to make sure important drugs, like anastrozole, will be available to women when it’s appropriate, providing support to help them make informed decisions about their options.

The researchers are warranting further accurate tests to predict which women will most benefit from anastrozole and those who will have the fewest side effects. This drug will also be a less toxic prevention alternative compared to other drugs like tamoxifen and raloxifene, which can increase the risk of blood clots and uterine cancer in women, according to the American Cancer Society. The less side effects the drug has, the more likely women will undergo cancer prevention treatment.

The National Cancer Institute reports there are more than 2.8 million breast cancer survivors in the U.S. A woman’s chance of having invasive breast cancer during her life is about one in eight and her chance of dying from the disease is about one in 36. However, breast cancer death rates have been decreasing due to early detection and better treatment.

To learn how to lower your risk of developing breast cancer, click here.

Source: Boanni B, Cawthron S, Cuzick J et al. Anastrozole for prevention of breast cancer in high-risk postmenopausal women (IBIS-II): an international, double-blind, randomised placebo-controlled trial. The Lancet. 2013.